Get tree visual elements WPF

WPF > Windows > Media > VisualTreeHelper 

VisualTreeHelper provides methods that perform

tasks involving nodes in a visual tree.

Example:

Get tree visual elements for user control

FrameworkElement fe = (FrameworkElement)YourControl;

for (int i = 0; i < VisualTreeHelper.GetChildrenCount(fe); i++)

{

   Grid childVisual = (Grid)VisualTreeHelper.GetChild(fe, i);

   childVisual.Width = sp.ActualWidth;

}